1. Field of the Invention
This invention relates to an accessing system for a network which includes a plurality of information terminal units (clients) and a center unit (server) which stores electronic mails from remote places or other electronic information for the client and performs calculations and processes of information for the client, and more particularly to an accessing system for a network used for requesting a server to perform access to information, access to electronic mail and do calculations by connection through which a radio unit such as a land mobile radio telephone set is used.
Here, the present invention doesn""t relate to an accessing system such as a leased data transmission path which is commonly used by a LAN (local area network) but to a data transmission path which uses a public network on which a radio unit such as a land mobile radio telephone is utilized.
It is to be noted that, in an access system which uses a leased data transmission path, the basic data transmission path is normally in a connected state between a client and a server such that data can normally be communicated between them.
On the other hand, in an access system on a data transmission path which uses a public network, the basic data transmission path is normally in a disconnected state, and immediately prior to communication of data, it is necessary for a client to dial up a server to connect a data transmission path.
In an access system which uses a public network, communication of data cannot be performed between a client and a server before a call is connected. In the procedure of utilizing a public network to connect a call, the process of dialing for connecting a call is sometimes performed by a server which dial up a client to connect the call.
The present invention relates to a method of automatically establishing a data transmission path, which uses a public network, between a client and a server and particularly relates to an accessing system for a network for communicating data on the data transmission path.
2. Description of the Related Art
In one conventionally available connection system of an access system in which a server connectable to a plurality of clients can be connected at any time with any client and transmit information or data requested by the client or receive information or data from the client which uses a public network is used to establish a data transmission path between the server and the client, a dial up connection system for connection of the public network is performed from the client side and the server authorizes the connection of the client. The server acknowledges the connection of the client and then communicates data, providing various services to the client.
Further, as an application of the dial up connection system, a call back connection system is available as disclosed in Japanese Patent Laid-Open No. 88469/1991 wherein, in order to reduce the burden of the connection charge of a public network on the client side, a call is originated from a client to a server and the server side requests the client to re-originate a call, and then the call is disconnected, whereafter a call is originated from the server side and authentication of the client is performed, and thereafter, data are communicated.
The two conventional methods described above are common in that a trigger for communication is provided from a client, and are widely known as methods wherein a server (remote access server: RAS) for which a public network is used to establish a connection is accessed by a client.
Also a procedure (protocol) for connection and transmission/reception of data has been laid open (for example, PPP: point to point protocolxe2x80x94RFC1331, RFC=xe2x80x9cRequest for commentxe2x80x9d). Any method wherein a client connects to a RAS presupposes that the client always provides the trigger for connection.
A method wherein a client connects to a RAS(Remote Access Server) as in the conventional examples described above has a problem in that, since it is presumed that the client will provide a trigger for connection, a data transmission request initiated by the server cannot be started at a time desired by the server.
If the server and the client have such a relationship that they are on a network wherein a data transmission path is normally in a connected state like a LAN (local area network), then a data transmission request initiated by the server can be started at any time desired intended by the server. However, in most of systems at present, in which a public network is used in order to establish a connection, the client side has the initiative in the connection timing.
The simplest solution would be a system constructed to provide a server function to the client. In short, the roles of the client and the server in the foregoing description would be reversed so that the client has the function of permitting connection from the server and communicating data after it acknowledges the connection of the server. This method can be devised readily from the prior art.
However, when the construction described above is employed, since the client authenticates a request for connection from the server, a false client cannot be discriminated. Therefore, there remains the problem of security on the server side.
Further, a device for accepting a connection and performing authentication must be provided on the client side. Consequently, the device would occupy a memory or a file on the client side. Particularly where the client is a portable radio information terminal of a small size it would be greatly disadvantages to be occupied by the device. Consequently, the problems described above must be solved with the client having a mechanism as simple as possible and by assuring security.
The present invention has the following objects.
A first object of the present invention is to provide a system wherein a dial up system used conventionally is used and, while the connection between a client and a server is maintained, the server side provides a trigger for communication. In short, the present invention proposes a method wherein, the server side requests the client to establish a connection at the time a request for communication is made.
A second object of the present invention is to provide a method of leveling resource loads at a server by managing and allocating in advance an access time to the server for each of clients registered.
A third object of the present invention is to provide a method of improving the operability for a user of a client by requesting, when a process requested by a client registered in advance is completed on the server side, the client to accept the results of the process.
A fourth object of the present invention is to provide a method by which, in response to a trigger from the outside to a client registered in advance such as arrival of mail, access can be requested anew from the client, thereby improving the operability for a user of the client.
A fifth object of the present invention is provide a method wherein a client can be requested to accept various resources such as a CPU resource and a file resource regarding a client registered in advance under the management of a server so that resources at the server can be saved.
In order to achieve the objects described above, in the present invention, communication data at a server to be sent to a client are sent to the client at a timing unique to the server by the following procedure.
The server has a table in which clients and telephone numbers are stored in a paired relationship in advance, and the server refers to the table when originating a telephone call to an object client.
At the time when a modem line is connected, the server sends to the client an identifier indicating a request for the client to access (for example, PPP connection) the server.
After reception of the request is confirmed, the client disconnects the modem line temporarily, and originates a telephone call to access the server. Then, the client accepts communication of data from the server, thereby receiving the data communication which the server intended to send the client.
The accessing system of a network according to the present invention has means which uses a protocol, simpler and has a smaller amount of communication than other protocols. This protocol is used to have the server send communication data to an arbitrary client to issue a connection request to a client so that the client can use a safe protocol conventionally used to connect to the server in order to accept communication data.
In the present invention having the construction described above, although, a conventional a dial up system is used and the client/server relationship is maintained, when a request for communication is made on the server side, a request for connection can be issued from the server side to the client side.
Further, access times to the server can be collectively managed and allocated from the server side to individual clients registered in advance.
Further, when processes requested from clients registered in advance are completed on the server side, the server can request the clients to accept the results of the processes.
Further, in response to a trigger from the outside for a client registered in advance, such as for arrival of mail, the server can request the client to access the server.
Further, the server can issue to a client registered in advance a request for acceptance of various resources such as a CPU and a file for the client under the management of the server.
The above and other objects, features and advantages of the present invention will become apparent from the following description with reference to the accompanying drawings which illustrate examples of the present invention.